Have you done anything with your gas injectors? They may get dirty/sticky if they don't get used regularly.

 

Yeah, but they get used at every startup for about 2 minutes. I also added an injector cleaner into the fuel tank and I also use 102 Aral Ultimate fuel only (no bio-ethanol in there to keep everything clean).

I will try to get a stethoscope and "listen" to the injectors maybe, also I will maybe unplug one and check if the engine "feels" and sounds the same.

But I really don't know what else to try...

 

So I drove to a workshop today, they are mainly doing Jeep but they have a Snap-On code reader.
As usual, while being there, the engine ran fine.
He found only one code, P0688.

I drove home and was driving on fuel (not LPG) to test.
After a few kilometers it started running bad again.
I plugged in my OBD reader and now it gave me P0307 again!

OK, now what to do?!
I think I will change the ignition coil over maybe? Remove spark plug? Or maybe some other wiring is bad?
Really annoying...

I also monitored something today. Everytime when the engine started that shaking the STFT1 went crazy high, like +20/+25. Once the engine ran fine it was back to normal and fluctuating around +/-5. So it looks like the PCM senses that one cylinder on bank 1 does not get enough fuel and tries to increase injector timing. That leads me even more to think that something is wrong with the wiring there. I will have to renew it all maybe to get rid of the problem. What do you think?